1.A local or subordinate law; a private law or regulation made by a corporation for its own government. "There was likewise a law to restrain the by-laws, or ordinances of corporations." "The law or institution; to which are added two by-laws, as a comment upon the general law."
2.A law that is less important than a general law or constitutional provision, and subsidiary to it; a rule relating to a matter of detail; as, civic societies often adopt a constitution and by-laws for the government of their members. In this sense the word has probably been influenced by by, meaning secondary or aside.
...